1. Field of the Invention
This invention relates generally to solid state color cameras, and more particularly to such a solid state color camera which employs a charge transfer device and specially designed color filters.
2. Description of the Prior Art
In devices using solid state sensors such as charge-coupled devices, hereinafter referred to as CCDs, as image pickup devices of a television camera, light information is converted into electrical signals which is sampled at every picture element. If it is assumed that the sampling frequency is f.sub.c, the alignment pitch, .tau..sub.H, of the picture elements in the horizontal direction is 1/f.sub.c. The electric charges stored in the respective picture elements are transferred to an output terminal at the rate of a clock pulse frequency and derived as a form of serial video signal. The resultant video signal S.sub.y contains DC components S.sub.DC and side band components S.sub.SB of sampling frequency f.sub.c modulated with the DC components S.sub.DC. In this case, there are upper and lower side band components S.sub.SB of the sampling frequency f.sub.c. If the frequency band of the DC component S.sub.DC is selected sufficiently wide so as to increase the resolution, higher band components S.sub.DH of the DC component S.sub.DC of the DC component S.sub. DC are superimposed on the side band component S.sub.SB of the sampling frequency f.sub.c and hence a sampling error results. If a picture is reproduced from the above video signal as it is, a flicker is caused in the reproduced picture. Since this is caused by the sampling error, the flicker can be avoided by restricting the frequency band of the DC component S.sub.DC to be smaller than one-half of the sampling frequency f.sub.c according to Nyquist's theorem. However, if the frequency band of the DC component S.sub.DC is restricted as above, the resolution is deteriorated. In order to make the frequency band of the DC component S.sub.DC about 3.5 MH.sub.Z without deteriorating the resolution and without sampling error, it is sufficient that the sampling frequency f.sub.c be selected sufficiently high. Since the sampling frequency f.sub.c is obtained by the product of n.sup.. f.sub.H (f.sub.c = n.sup.. f.sub.H) where n is the number of picture elements in the horizontal direction of the CCDs and f.sub.H is the horizontal frequency of the television signal, if the sampling frequency f.sub.c is made high enough to remove the sampling error, the number n of the picture elements must be increased correspondingly, with the result that the manufacturing of the CCDs becomes costly.
Further, since three color filters or R(red), G(green) and B(blue) stripe color filter elements are used so as to form a color camera, the frequency of carriers for the respective color components is lowered to 1/3.sup.. f.sub.c. Accordingly, a sampling error is caused over all the band of the DC component S.sub.DC, resulting in a reproduced picture of less than the desired quality.